The books were never black and white, that is what lord of the rings was criticized for. There is never bad and good guys, just reaction to events. I think it would be intersting to see the bad side of the elves. See how easily their pride is hurt...

The reason the Goblins goes for the treasure should be because of a combination of:

-Necromancer's wishes -Gandalf killing Goblin King

And also you are suggesting the goblins would hunt them inside mirkwood? The goblins would never enter Mirkwood, they hate the forests. Especially when they are inhabited by elves.